Swirler, burner and combustor for a gas turbine engine

ABSTRACT

A swirler for use in a combustor of a gas turbine engine, having a plurality of generally radially inwardly extending passages arranged circumferentially staggered in a circle, each passage having a radially outer inlet end, a radially inner outlet end, first and second generally radially inwardly extending lateral surfaces, and a base surface and top surface, in use of the swirler fuel and air travelling along the passages from their inlet ends to their outlet ends so as to create adjacent to the outlet ends a swirling fuel/air mixture. At least one surface of at least one passage has at least one gas fuel injection hole, wherein the surface, having the gas fuel injection hole, has at least one counterbore radially surrounding the gas fuel injection hole, wherein the gas fuel injection hole is arranged at a base of the counterbore.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2016/055802 filed Mar. 17, 2016, and claims the benefit thereof. The International Application claims the benefit of European Application No. EP15162154 filed Apr. 1, 2015. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a swirler for use in a combustor of a gas turbine engine, comprising a plurality of generally radially inwardly extending passages arranged circumferentially staggered in a circle, each passage having a radially outer inlet end, a radially inner outlet end, first and second generally radially inwardly extending lateral surfaces, and a base surface and top surface, in use of the swirler fuel and air travelling along the passages from their inlet ends to their outlet ends so as to create adjacent to the outlet ends a swirling fuel/air mixture, wherein at least one surface comprises at least one gas fuel injection hole.

Moreover, the invention relates to a burner for a gas turbine engine.

Furthermore, the invention relates to a combustor for a gas turbine engine.

BACKGROUND OF INVENTION

A gas turbine engine comprises an ambient air supply duct, a compressor, a combustor, an expander, i.e. a turbine, and an exhaust gas duct.

It is desired to reduce the polluting emissions, in particular nitrogen oxide (NO_(x)), carbon monoxide (CO), unburned hydro carbons (UHC), smoke and particle emissions, of gas turbine engines.

One way to reduce polluting emissions is to provide a burner in a combustor of a gas turbine engine with a swirler. The swirler is arranged in a passage through which compressed air is supplied to a combustion chamber of the combustor via the burner. The swirler is connected to a gas fuel supply device. The swirler gives the supplied air a tangential direction rotating the flow i.e. providing a swirling air flow to the combustion chamber. Simultaneously, gas fuel is introduced in the air through internal gas fuel passages arranged in the swirler. The swirling air/gas fuel mixture is supplied to the combustion chamber of the combustor. The swirling of the air/gas fuel mixture leads to a highly homogeneous air/gas fuel mixture in form of a lean gas fuel mixture. Such lean gas fuel mixtures burn at a lower combustion temperatures than rich gas fuel mixtures. Reduced combustion temperatures particularly lead to reduced nitrogen oxide emissions.

EP 1 867 925 A1 discloses a burner, in particular a gas turbine burner, comprises at least one swirler. The swirler having at least one air inlet opening, at least one air outlet opening positioned downstream to the air inlet opening and at least one swirler air passage) extending from the at least one air inlet opening to the at least one air outlet opening which is delimited by swirler air passage walls. The air passage walls comprising downstream wall sections adjoining the at least one air outlet opening; and a fuel injection system which comprises fuel injection openings arranged in at least one swirler air passage wall so as to inject fuel into the swirler air passage; in which at least the downstream section of one air passage wall is corrugated.

US2010/011770 A1 discloses a premixer for a gas turbine combustor includes an axial swirler including a plurality of turning vanes that impart swirl velocity to an axial airflow through the premixer and at least one fuel injection site enabling fuel to mix with the airflow in the premixer. The fuel injection site terminates in a cratered hole. The cratered hole increases mixing efficiency and increases flashback/flameholding resistance.

US2012/0111015A1 discloses a combustor having a radial swirler type burner wherein an air/fuel mixture is forced into a vortex by the swirler before being burned in the main combustor chamber. The radial swirler comprises an annular array of vanes that form air passages therebetween. The air passages are arranged generally radially inwardly to create a vortex. Fuel is mixed with the air in the passages.

SUMMARY OF INVENTION

It is an object of the invention to further reduce polluting emissions, in particular nitrogen oxide emissions, associated with the operation of gas turbine engines.

This object is solved by the independent claims. Advantageous embodiments are disclosed in the dependent claims which either by taken alone or in any combination with each other may relate to an aspect of the invention.

The swirler according to the invention for use in a combustor of a gas turbine engine comprises a plurality of generally radially inwardly extending passages arranged circumferentially staggered in a circle, each passage having a radially outer inlet end, a radially inner outlet end, first and second generally radially inwardly extending lateral surfaces, and a base surface and top surface, in use of the swirler fuel and air travelling along the passages from their inlet ends to their outlet ends so as to create adjacent to the outlet ends a swirling fuel/air mixture, wherein at least one surface of at least one passage comprises at least one gas fuel injection hole, wherein the surface, having the gas fuel injection hole, comprises at least one counterbore radially surrounding the gas fuel injection hole, and wherein the gas fuel injection hole is arranged at a base of the counterbore.

According to the invention the gas fuel injection hole is not arranged, as conventionally known, directly at the surface of the passage, but in the counterbore of the surface which defines a cavity in the surface. Through this, a low velocity region is created in the cavity, i.e. the counterbore, to reduce the momentum of a gas fuel jet exiting the gas fuel injection hole. Thereby, the incoming cross flow of air inside the cavity will mix with local recirculation in the cavity to enhance mixing of air and gas fuel. This enhanced or tailored mixing is attended by lower polluting emissions. Additionally, the enhanced or tailored mixing results in a reduction of the number of hot spots to further reduce pollution emissions.

Particularly, the cross flow velocity of compressed air streaming along the surface of the passage comprising the counterbore reduces the momentum of the gas fuel stream exiting the gas fuel injection hole by recirculation of air with low pressure inside the counterbore. Through this, the aerodynamics for mixing gas fuel and air are improved.

In contrast, known swirlers comprise passages with gas fuel injection holes directly arranged for example at a lateral surface which is defined by a lateral surface plane of a vane of the swirler without providing an inventive counterbore. This leads to less efficient and/or controlled mixing of gas fuel and air because the gas fuel streams coming from the gas fuel injection holes travel toward an expansion region of the combustion chamber of the combustor without being effectively influenced by mixing.

The inventive swirler can have one or more passages designed according to the invention. Especially, all passages of the swirler can be designed accordingly. The cross section of at least one passage can be rectangular, squared, circular, elliptical or the like.

The surface of the at least one swirler passage according to the invention can have two or more gas fuel injection holes. Each gas fuel injection hole communicates with at least one internal gas supply passage of the swirler. At least one surface can be flat-shaped, leaning, facet-shaped, curved-shaped or the like.

The counterbore can be optimized with respect to its mixing characteristics. For example the dimensions of the counterbore, such as its depth, diameter or the like, can be adapted to a specific use of the swirler in order to optimize the mixing characteristics of the swirler.

Advantageously, the counterbore is rectangular-shaped, oval-shaped, elliptical-shaped or circular-shaped. Other shapes of the counterbore are also possible to improve the mixing characteristics of the counterbore.

Advantageously, at least one surface comprises at least two gas fuel injection holes and at least one counterbore, the counterbore radially surrounding both gas fuel injection holes, wherein the gas fuel injection holes are arranged at a base of the counterbore. According to this, all gas fuel injection holes of a surface can be arranged in a common single counterbore of that surface.

Advantageously, wherein at least one surface comprises at least two gas fuel injection holes and at least two counterbores, wherein each gas fuel injection hole is radially surrounded by its own counterbore and is arranged at a base of this counterbore. According to this embodiment, more than one counterbore is arranged on one single surface of the swirler passage, each counterbore surrounding at least one gas fuel injection hole.

Advantageously, the surface, having the at least one gas fuel injection hole and the at least one counterbore, is a lateral surface. The lateral surface can be defined by a lateral surface of a vane of the swirler.

Advantageously, the surface, having the at least one gas fuel injection hole and the at least one counterbore, is the base surface.

The burner according to the invention for a gas turbine engine comprises at least one swirler according to any one of the preceding embodiments or any combination thereof. The above mentioned advantages connected with the swirler are correspondingly connected with the inventive burner.

The combustor according to the invention for a gas turbine engine comprises at least one burner according to the invention. The above mentioned advantages connected with the swirler are correspondingly connected with the inventive combustor.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned attributes and other features and advantages of this invention and the manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein

FIG. 1 shows part of a turbine engine in a sectional view,

FIG. 2 shows a longitudinal section through a combustor of the turbine engine,

FIG. 3 shows a perspective view of an inventive swirler of the combustor,

FIG. 4 shows a perspective transparent drawing of a detail of an embodiment of the inventive swirler,

FIG. 5 shows a sectional view of the swirler shown in FIG. 4,

FIG. 6 shows a perspective transparent drawing of a detail of a further embodiment of the inventive swirler,

FIG. 7 shows a perspective transparent drawing of a detail of a further embodiment of the inventive swirler, and

FIG. 8 shows a perspective transparent drawing of a detail of a further embodiment of the inventive swirler.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 is a schematic illustration of a general arrangement of a gas turbine engine 10 having an inlet 12, a compressor 14, a combustor system 16, a turbine system 18, an exhaust duct 20 and a twin-shaft arrangement 22, 24. The gas turbine engine 10 is generally arranged about an axis 26 which for rotating components is their rotational axis. The arrangements 22, 24 may have the same or opposite directions of rotation.

The combustion system 16 comprises an annular array of combustor units, i.e. burner 36, only one of which is shown. In one example, there are six burners 36 evenly spaced about the engine 10.

The turbine system 18 includes a high-pressure turbine 28 drivingly connected to the compressor 14 by a first shaft 22 of the twin-shaft arrangement 22, 24. The turbine system 18 also includes a low-pressure turbine 30 drivingly connected to a load (not shown) via a second shaft 24 of the twin-shaft arrangement.

The term axial is with respect to the axis 26. The terms upstream and downstream are with respect to the general direction of gas flow through the engine 10 and as seen in FIG. 1 is generally from left to right.

The compressor 14 comprises an axial series of stator vanes and rotor blades mounted in a conventional manner. The stator or compressor vanes may be fixed or have variable geometry to improve the airflow onto the downstream rotor or compressor blades.

Each turbine 28, 30 comprises an axial series of stator vanes and rotor blades mounted via rotor discs arranged and operating in a conventional manner. A rotor assembly comprises an annular array of rotor blades or blades and the rotor disc.

In operation air 32 is drawn into the engine 10 through the inlet 12 and into the compressor 14 where the successive stages of vanes and blades compress the air before delivering the compressed air into the combustion system 16. In a combustion chamber of the combustion system 16 the mixture of compressed air and fuel is ignited. The resultant hot working gas flow is directed into, expands and drives the high-pressure turbine 28 which in turn drives the compressor 14 via the first shaft 22. After passing through the high-pressure turbine 28, the hot working gas flow is directed into the low-pressure turbine 30 which drives the load via the second shaft 24.

The low-pressure turbine 30 can also be referred to as a power turbine and the second shaft 24 can also be referred to as a power shaft. The load is typically an electrical machine for generating electricity or a mechanical machine such as a pump or a process compressor. Other known loads may be driven via the low-pressure turbine 30. The fuel may be in gaseous and/or liquid form.

The turbine engine 10 shown and described with reference to FIG. 1 is just one example of a number of engines or turbomachinery in which this invention can be incorporated. Such engines can be gas turbines or steam turbine and include single, double and triple shaft engines applied in marine, industrial and aerospace sectors.

FIG. 2 shows a longitudinal section through a combustor 100 of the gas turbine engine. The combustor 100 comprises in flow direction series a burner 131 with swirler portion 102 and a burner-head portion 101 attached to the swirler portion 102, a transition piece or combustion pre-chamber 103 and a main combustion chamber 104. The main combustion chamber 104 has a diameter larger than the diameter of the pre-chamber 103. The main combustion chamber 104 is connected to the pre-chamber 103 via a dome portion 110 comprising a dome plate 111 and which is divergent in the direction from the pre-chamber 103 to the main combustion chamber 104. In general, the pre-chamber 103 may be implemented as a one part continuation of the burner 101 towards the combustion chamber 104, as a one part continuation of the combustion chamber 104 towards the burner 101, or as a separate part between the burner 101 and the combustion chamber 104. The burner and the combustion chamber assembly generally symmetrical about a longitudinal axis S.

A fuel conduit 105 is provided for leading a gaseous or liquid fuel to the burner which is to be mixed with in-streaming air in the swirler 102. The fuel/air mixture 107 is then led towards the primary combustion zone 109 where it is burnt to form hot, pressurised exhaust gases streaming in a direction 108 indicated by arrows to a turbine of the gas turbine engine.

An exemplary swirler 102 according to the present invention is shown in detail in FIG. 3. The swirler 102 comprises an annular array of swirler vanes 112 and in this example there are twelve swirler vanes 112 arranged on a swirler vane support 113 or plate.

Between neighbouring swirler vanes 112 air passages 114 are formed. The air passages 114 extend between an air inlet opening 116 and an air outlet opening 118. The air passages 114 are defined by opposing side faces 120, 122 of the neighbouring swirler vanes 112, by the surface 124 of the swirler vane plate 113. The side faces 120, 122, the surfaces of the swirler vane plate 113 and form the air passage walls defining the air passages 114. A further plate or part of the combustor is situated on the opposite end surface of the swirler vanes to the support plate and therefore completes the definition of the air passages 114.

The side faces 120, 122 are corrugated in their downstream sections so as to form mixing lobes 123 on the swirler vanes 112. The corrugations of opposing side faces 120, 122 are complementary so as to lead to additional turbulence in the streaming fuel/air mixture and to a controlled fuel placement at the exit of the air passage. In other examples, the downstream or trailing edge of the swirler vanes 112 can be straight.

Fuel injection openings 126 a, 126 b are arranged in the side faces 120. Further, fuel injection openings 128 are arranged in the swirler support 113. The fuel injection openings 126 a, 126 b, 128 are pilot and main fuel injectors as known in the art. During operation of the burner, air flows into the air passages 114 through the air inlet openings 116. Within the air passages 114 fuel is injected into the streaming air by use of fuel injection openings 126 a, 126 b, 128. The fuel/air mixture then leaves the air passages 114 through the air outlet openings 118 and streams through a central opening 130 of the swirler vane array and into the pre-chamber 103. From the pre-chamber 103 it streams into the combustion zone 109 of the main chamber 104 where it is burned. As shown in FIG. 4, there are arranged two first fuel injection openings in the side faces 120 of the swirler vanes 112 so to define bottom and top first fuel injection openings 126 a. Alternative locations of the fuel injection openings are shown as 126 b.

FIG. 4 shows a perspective transparent drawing of a detail of an embodiment of the inventive swirler 1 for use in a combustor of a gas turbine engine.

The swirler 102 comprises a plurality of generally radially inwardly extending passages 114 arranged circumferentially staggered in a circle, wherein only one passage 114 is shown in FIG. 4. The radially inwardly extending air passages 114 could also be said to be arranged tangential to a radius from the axis S of the swirler. The swirler is known as a radial swirler and its air passages 114 are arranged so that a component of their direction is in the radial direction. Each passage 114 having a radially outer inlet end 116 and a radially inner outlet end 118, which are shown in FIG. 3. Each passage 114 is defined by surfaces 3, wherein only one surface 3 is shown in FIG. 4. This surface 3 may be a lateral or side surface 120, 122, a base surface 124 or a top surface. In use of the swirler 1 fuel and air travelling along the passages 114 from their inlet ends to their outlet ends so as to create adjacent to the outlet ends a swirling fuel/air mixture.

The surface 3 comprises two gas fuel injection holes 5 communicating with an internal gas fuel supply passage 4 of the swirler 102. Additionally, the surface 3 comprises a rectangular-shaped, in particular box-shaped, counterbore 6 radially surrounding the gas fuel injection holes 5. The gas fuel injection holes 5 are arranged at a base 38 of the counterbore 6. Therefore, the common counterbore 6 radially surrounds both gas fuel injection holes 5. The flow of gas fuel through the gas fuel supply passage 4 is indicated by the arrow 7.

FIG. 5 shows a section view of the swirler 102 shown in FIG. 3. The air streaming along the surface 3 is indicated by the arrow 8. The spirally-shaped lines 9 indicate how air circulates in said counterbore 6, thereby reducing the momentum of a gas fuel jet exiting the gas fuel injection holes 5. The incoming cross flow of air inside the counterbore 6 will mix with these local recirculation in the counterbore 6, thereby enhancing the mixing of air and gas fuel.

The embodiment of the counterbore 6 shown in FIGS. 4 and 5 is generally rectangular and has a depth D below the surface 3, a width W normal to the direction of the air flow 8 and a length L generally in line with the direction of the air flow 8. The gas fuel injection holes 5 have a diameter d. In this embodiment, advantageous relative parameters to the diameter d are length L at least 4d; width W at least 3d and depth D at least 2d. These minimum relative dimensions are known to provide the advantages mentioned below.

FIG. 6 shows a perspective transparent drawing of a detail of a further embodiment of the inventive swirler 102. This embodiment differs from the embodiment shown in FIG. 4 only in that the counterbore 6 is oval-shaped.

The embodiment of the counterbore 6 shown in FIG. 6 is generally oval-shaped with its longer dimension a generally in line with the direction of the air flow 8. The shorter dimension b is general normal to the direction of the air flow 8 and the longer dimension a. The counterbore 6 has a depth D below the surface 3. The gas fuel injection holes 5 have a diameter d. In this embodiment, advantageous relative parameters to the diameter d are longer dimension a is at least 4d; shorter dimension W is at least 3d and depth D is at least 2d. These minimum relative dimensions are known to provide the advantages mentioned below.

FIG. 7 shows a perspective transparent drawing of a detail of a further embodiment of the inventive swirler 102. This embodiment differs from the embodiment shown in FIG. 4 only in that the counterbore 6 is circular-shaped.

The circular-shaped embodiment of the counterbore 6 shown in FIG. 7 has a depth D below the surface 3 and a diameter L. The gas fuel injection holes 5 have a diameter d. In this embodiment, advantageous relative parameters to the diameter d are diameter L is at least 4d and the depth D is at least 2d. These minimum relative dimensions are known to provide the advantages mentioned below.

FIG. 8 shows a perspective transparent drawing of a detail of a further embodiment of the inventive swirler 102. This embodiment differs from the embodiments shown in FIG. 4 to FIG. 7 in that the surface 3 comprises two gas fuel injection holes 5 and two counterbores 6, wherein each gas fuel injection hole 5 is radially surrounded by its own counterbore 6 and is arranged at a base 38 of this counterbore 6.

Each of the two counterbores 6 can be any one of the circular, rectangular or oval shaped counterbores 6 described above. However, in this embodiment, advantageous relative parameters to the diameter d are diameter L (or longer dimension L) is at least 2d and the depth D is at least 2d. In addition, the spacing X between the counterbores 6 is at least 2d.

In the described embodiments, the gas fuel injection holes 5 are arranged in a row with respect to the flow direction, indicated by the arrow 8, of air streaming along the surface 3. Alternatively, the gas fuel injection holes 5 may be arranged in a crosswise direction with respect to said flow direction.

The advantages of the embodiments of the counterbores and their location on the side surfaces of the swirler vanes 112 include reducing local hot spots, reduced NOx emissions by improved mixing of fuel and air and improved fuel placement. The mixing of fuel and air that flows across the side surface improves because of the local lowering of fuel momentum in the counterbore. Thus the local fuel-air ratio provided by the counterbores is closer to the local stoichiometric mixture fraction than other fuel injection means.

Although the invention has been explained and described in detail in connection with the preferred embodiments it is noted that the invention is not limited to the disclosed embodiments. A person skilled in the art can derive from these embodiments other variations without leaving the scope of protection of the invention. 

1. A swirler for use in a combustor of a gas turbine engine, the swirler comprising: an axis and an annular array of swirler vanes arranged about the axis and at least partly defining a plurality of generally radially inwardly extending passages arranged to create a vortex of fuel and air about the axis, wherein each passage has a radially outer inlet end, a radially inner outlet end, first and second generally radially inwardly extending lateral surfaces, so that in use of the swirler, fuel and air travelling along the passages from their inlet ends to their outlet ends create adjacent to the outlet ends a swirling fuel/air mixture, wherein at least one lateral surface comprises at least one gas fuel injection hole, wherein the surface, having the gas fuel injection hole, comprises at least one counterbore radially surrounding the gas fuel injection hole.
 2. The swirler according to claim 1, wherein the counterbore is rectangular-shaped, oval-shaped, elliptical-shaped or circular-shaped.
 3. The swirler according to claim 1, wherein at least one surface comprises at least two gas fuel injection holes and at least one counterbore, the counterbore radially surrounding both gas fuel injection holes, wherein the gas fuel injection holes are arranged at a base of the counterbore.
 4. The swirler according to claim 3, wherein two counterbores are spaced apart a distance X and the distance X is at least 2d, where d is the diameter of gas fuel injection holes.
 5. The swirler according to claim 4, wherein the counterbores have a dimension L and L is at least 2d and a depth D of the counterbore is at least 2d.
 6. The swirler according to claim 1, wherein at least one surface comprises at least two gas fuel injection holes and at least two counterbores, wherein each gas fuel injection hole is radially surrounded by its own counterbore and is arranged at a base of this counterbore.
 7. The swirler according to claim 1, wherein the surface, having the at least one gas fuel injection hole and the at least one counterbore is a lateral surface.
 8. The swirler according to claim 1, wherein the surface, having the at least one gas fuel injection hole and the at least one counterbore is the base surface.
 9. The swirler according to claim 1, wherein the counterbore has a depth D below the surface, a width W normal to the direction of an air flow across the surface and a length L generally in line with the direction of the air flow, the gas fuel injection hole has a diameter d; wherein the length L is at least 4d and/or the width W is at least 3d and/or the depth D is at least 2d.
 10. A burner for a gas turbine engine, comprising: at least one swirler according to claim
 1. 11. A combustor for a gas turbine engine, comprising: at least one burner according to claim
 10. 